vegan (version 2.0-10)

ordiresids: Plots of Residuals and Fitted Values for Constrained Ordination

Description

The function provides plot.lm style diagnostic plots for the results of constrained ordination from cca, rda and capscale. Normally you do not need these plots, because ordination is descriptive and does not make assumptions on the distribution of the residuals. However, if you permute residuals in significance tests (anova.cca), you may be interested in inspecting that the residuals really are exchangeable and independent of fitted values.

Usage

ordiresids(x, kind = c("residuals", "scale", "qqmath"),
   residuals = "working", type = c("p", "smooth", "g"),
   formula, ...)

Arguments

x

Ordination result from cca, rda or capscale.

kind

The type of plot: "residuals" plot residuals against fitted values, "scale" the square root of absolute residuals against fitted values, and "qqmath" the residuals against expected distribution (defaults

residuals

The kind of residuals and fitted values. The argument is passed on to fitted.cca with alternatives "working" and "response".

type

The type of plot. The argument is passed on to lattice functions.

formula

Formula to override the default plot. The formula can contain items Fitted, Residuals, Species and Sites (provided that names of species and sites are available in the ordination result).

...

Other arguments passed to lattice functions.

Value

• The function return a Lattice object that can displayed as plot.

Details

The default plots are similar as in plot.lm, but they use Lattice functions xyplot and qqmath. The alternatives have default formulae but these can be replaced by the user. The elements available in formula or in the groups argument are Fitted, Residuals, Species and Sites.

See Also

plot.lm, Lattice, xyplot, qqmath.

Examples

data(varespec)
data(varechem)
mod <- cca(varespec ~ Al + P + K, varechem)
ordiresids(mod)